This detection rule monitors changes to a specific Windows registry key, namely "HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon\SpecialAccounts\Userlist". When the value of this key is set to "0", it indicates that a user account is hidden from the Windows logon screen, preventing it from being displayed during the authentication process. This behavior is often associated with evasion tactics used by attackers who aim to conceal their unauthorized access or maintain persistence on a compromised system. The rule utilizes EventType 'SetValue' to capture these modifications and checks that the relevant target object contains the specified registry path. Given the intent behind hiding a user account, the rule assigns a high alert level, indicating its potential significance in threat detection. Although this rule can generate valid detection signals, there may be instances where legitimate changes occur, categorized as false positives, leading to the uncertainty noted in our false positive assessments.